A Comprehensive Study to Determine the Residual Elimination Pattern of Major Metabolites of Amoxicillin-Sulbactam Hybrid Molecules in Rats by UPLC-MS/MS.

Amoxicillin and sulbactam are widely used in animal food compounding. Amoxicillin-sulbactam hybrid molecules are bicester compounds made by linking amoxicillin and sulbactam with methylene groups and have good application prospects. However, the residual elimination pattern of these hybrid molecules in animals needs to be explored. In the present study, the amoxicillin-sulbactam hybrid molecule (AS group) and a mixture of amoxicillin and sulbactam (mixture group) were administered to rats by gavage, and the levels of the major metabolites of amoxicillin, amoxicilloic acid, amoxicillin diketopiperazine, and sulbactam were determined by UPLC-MS/MS. The residue elimination patterns of the major metabolites in the liver, kidney, urine, and feces of rats in the AS group and the mixture group were compared. The results showed that the total amount of amoxicillin, amoxicilloic acid, amoxicillin diketopiperazine, and the highest concentration of sulbactam in the liver and kidney samples of the AS group and the mixture group appeared at 1 h after drug withdrawal. Between 1 h and 12 h post discontinuation, the total amount of amoxicillin, amoxicilloic acid, and amoxicillin diketopiperazine in the two tissues decreased rapidly, and the elimination half-life of the AS group was significantly higher than that in the mixture group (p < 0.05); the residual amount of sulbactam also decreased rapidly, and the elimination half-life was not significantly different (p > 0.05). In 72 h urine samples, the total excretion rates were 60.61 ± 2.13% and 62.62 ± 1.73% in the AS group and mixture group, respectively. The total excretion rates of fecal samples (at 72 h) for the AS group and mixture group were 9.54 ± 0.26% and 10.60 ± 0.24%, respectively. These results showed that the total quantity of amoxicillin, amoxicilloic acid, and amoxicillin diketopiperazine was eliminated more slowly in the liver and kidney of the AS group than those of the mixture group and that the excretion rate through urine and feces was essentially the same for both groups. The residual elimination pattern of the hybrid molecule in rats determined in this study provides a theoretical basis for the in-depth development and application of hybrid molecules, as well as guidelines for the development of similar drugs.

In Vitro Characterization of Polysaccharides from Fresh Tea Leaves in Simulated Gastrointestinal Digestion and Gut Microbiome Fermentation.

Tea plants have a long cultivation history in the world, but there are few studies on polysaccharides from fresh tea leaves. In this study, tea polysaccharides (TPSs) were isolated from fresh tea leaves. Then, we investigated the characteristics of TPSs during in vitro simulated digestion and fermentation; moreover, the effects of TPSs on gut microbiota were explored. The results revealed that saliva did not significantly affect TPSs' molecular weight, monosaccharide composition, and reducing sugar content, indicating that TPSs cannot be digested in the oral cavity. However, TPSs were partially decomposed in the gastrointestinal tract after gastric and intestinal digestion, resulting in the release of a small amount of free glucose monosaccharides. Our in vitro fermentation experiments demonstrated that TPSs are degraded by gut microbiota, leading to short-chain fatty acid (SCFA) production and pH reduction. Moreover, TPSs increased the abundance of Bacteroides, Lactobacillus, and Bifidobacterium but reduced that of Escherichia, Shigella, and Enterococcus, demonstrating that TPSs can regulate the gut microbiome. In conclusion, TPSs are partially decomposed by gut microbiota, resulting in the production of SCFAs and the regulation of gut microbiota composition and function. Therefore, TPSs may be used to develop a prebiotic supplement to regulate the gut microbiome and improve host health.

Synergism with Shikimic Acid Restores ß-Lactam Antibiotic Activity against Methicillin-Resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved into a dangerous pathogen resistant to beta-lactam antibiotics (BLAs) and has become a worrisome superbug. In this study, a strategy in which shikimic acid (SA), which has anti-inflammatory and antibacterial activity, is combined with BLAs to restart BLA activity was proposed for MRSA treatment. The synergistic effects of oxacillin combined with SA against oxacillin resistance in vitro and in vivo were investigated. The excellent synergistic effect of the oxacillin and SA combination was confirmed by performing the checkerboard assay, time-killing assay, live/dead bacterial cell viability assay, and assessing protein leakage. SEM showed that the cells in the control group had a regular, smooth, and intact surface. In contrast, oxacillin and SA or the combination treatment group exhibited different degrees of surface collapse. q-PCR indicated that the combination treatment group significantly inhibited the expression of the mecA gene. In vivo, we showed that the combination treatment increased the survival rate and decreased the bacterial load in mice. These results suggest that the combination of oxacillin with SA is considered an effective treatment option for MRSA, and the combination of SA with oxacillin in the treatment of MRSA is a novel strategy.

Alkaline arginine promotes the gentamicin-mediated killing of drug-resistant Salmonella by increasing NADH concentration and proton motive force.

Introduction: Antimicrobial resistance, especially the development of multidrug-resistant strains, is an urgent public health threat. Antibiotic adjuvants have been shown to improve the treatment of resistant bacterial infections. Methods: We verified that exogenous L-arginine promoted the killing effect of gentamicin against Salmonella in vitro and in vivo, and measured intracellular ATP, NADH, and PMF of bacteria. Gene expression was determined using real-time quantitative PCR. Results: This study found that alkaline arginine significantly increased gentamicin, tobramycin, kanamycin, and apramycin-mediated killing of drug-resistant Salmonella, including multidrug-resistant strains. Mechanistic studies showed that exogenous arginine was shown to increase the proton motive force, increasing the uptake of gentamicin and ultimately inducing bacterial cell death. Furthermore, in mouse infection model, arginine effectively improved gentamicin activity against Salmonella typhimurium. Discussion: These findings confirm that arginine is a highly effective and harmless aminoglycoside adjuvant and provide important evidence for its use in combination with antimicrobial agents to treat drug-resistant bacterial infections.

Genomic analysis and characterization of bacteriophage vB_SpuS_NX263 infecting Salmonella enterica subsp. enterica serovar Pullorum.

In this study, a new Salmonella phage, NX263, was isolated from sewage. This phage could lyse 90.57% (48/53) of the bacterial strains tested and showed good activity over a wide range of temperature (up to 60°C) and pH (5-10). Phylogenetic analysis showed that it should be classified as a member of the genus Skatevirus. The genome of phage NX263 is 46,574 bp in length with a GC content of 45.52%. It contains 89 open reading frames and two tRNA genes. No lysogeny, drug resistance, or virulence-associated genes were identified in the genome sequence, suggesting that this phage could potentially be used to treat Salmonella Pullorum infections.

L-leucine increases the sensitivity of drug-resistant Salmonella to sarafloxacin by stimulating central carbon metabolism and increasing intracellular reactive oxygen species level.

Introduction: The overuse of antibiotics has made public health and safety face a serious cisis. It is urgent to develop new clinical treatment methods to combat drug resistant bacteria to alleviate the health crisis. The efficiency of antibiotics is closely related to the metabolic state of bacteria. However, studies on fluoroquinolone resistant Salmonella are relatively rare. Methods: CICC21484 were passaged in medium with and without sarafloxacin and obtain sarafloxacin- susceptible Salmonella Typhimurium (SAR-S) and sarafloxacin resistant Salmonella Typhimurium (SAR-R), respectively. Non-targeted metabolomics was used to analyze the metabolic difference between SAR-S and SAR-R. Then we verified that exogenous L-leucine promoted the killing effect of sarafloxacin in vitro, and measured the intracellular ATP, NADH and reactive oxygen species levels of bacteria. Gene expression was determined using Real Time quantitative PCR. Results: We confirmed that exogenous L-leucine increased the killing effect of sarafloxacin on SAR-R and other clinically resistant Salmonella serotypes. Exogenous L-leucine stimulated the metabolic state of bacteria, especially the TCA cycle, which increased the working efficiency of the electron transfer chain and increased the intracellular NADH, ATP concentration, and reactive oxygen species level. Our results suggest that when the metabolism of drug-resistant bacteria is reprogrammed, the bactericidal effect of antibiotics improves. Discussion: This study further enhances research in the anti-drug resistance field at the metabolic level and provides theoretical support for solving the current problem of sarafloxacin drug resistance, a unique fluoroquinolone drug for animals and indicating the potential of L-leucine as a new antibiotic adjuvant.

Exogenous D-ribose promotes gentamicin treatment of several drug-resistant Salmonella.

The metabolic microenvironment of bacteria impacts drug efficacy. However, the metabolic mechanisms of drug-resistant Salmonella spp. remain largely unknown. This study characterized the metabolic mechanism of gentamicin-resistant Salmonella Choleraesuis and found that D-ribose increased the gentamicin-mediated killing of this bacteria. Non-targeted metabolomics of homologous gentamicin-susceptible Salmonella Choleraesuis (SCH-S) and gentamicin-resistant S. Choleraesuis (SCH-R) was performed using UHPLC-Q-TOF MS. The metabolic signature of SCH-R included disrupted central carbon metabolism and energy metabolism, along with dysregulated amino acid and nucleotide metabolism, vitamin and cofactor metabolism, and fatty acid synthesis. D-ribose, the most suppressed metabolite in SCH-R, was shown to strengthen gentamicin efficacy against SCH-R and a clinically isolated multidrug-resistant strain. This metabolite had a similar impact on Salmonella. Derby and Salmonella. Typhimurium. D-ribose activates central carbon metabolism including glycolysis, the pentose phosphate pathway (PPP), and the tricarboxylic acid cycle (TCA cycle), increases the abundance of NADH, polarizes the electron transport chain (ETC), and elevates the proton motive force (PMF) of cells, and induces drug uptake and cell death. These findings suggest that central carbon metabolism plays a critical role in the acquisition of gentamicin resistance by Salmonella, and that D-ribose may serve as an antibiotic adjuvant for gentamicin treatment of resistant bacterial infections.

A Comprehensive Study to Identify Major Metabolites of an Amoxicillin-Sulbactam Hybrid Molecule in Rats and Its Metabolic Pathway Using UPLC-Q-TOF-MS/MS.

Amoxicillin and sulbactam are widely used compound drugs in animal food. The amoxicillin-sulbactam hybrid molecule can achieve better curative effects through the combination of the two drugs. However, its pharmacokinetic behavior needs to be explored. In this study, a randomized crossover experiment was performed to investigate the metabolism of the novel amoxicillin-sulbactam hybrid molecule in rats after gastric administration. Ultrahigh performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS) was used to isolate and to identify the metabolites in rats. Amoxicillin, amoxicilloic acid, amoxicillin diketopiperazine, and sulbactam were eventually detected in the plasma, liver, urine, and kidneys; no hybrid molecules and their metabolites were detected in feces. The in vivo metabolism results showed that the hybrid molecule was absorbed into the body in the intestine, producing amoxicillin and sulbactam, then amoxicillin was partially metabolized to amoxicilloic acid and amoxicillin diketopiperazine, which are eventually excreted in the urine by the kidneys. In this study, four major metabolites of the amoxicillin-sulbactam hybrid molecule were identified and their metabolic pathways were speculated, which provided scientific data for understanding the metabolism of the hybrid molecule and for its clinical rational use.

Ginsenoside Rg1 Mitigates Porcine Intestinal Tight Junction Disruptions Induced by LPS through the p38 MAPK/NLRP3 Inflammasome Pathway.

Inflammation leads to porcine tight junction disruption of small intestinal epithelial cells, resulting in intestinal dysfunction. Herein, we established lipopolysaccharide (LPS)-induced in-vivo and in-vitro inflammatory models. The results revealed that LPS induced tight junction disruption in IPEC-J2 cells by downregulating tight-junction-related protein zonula occludens-1 (ZO-1), occludin and claudin-1 expression, while ginsenoside Rg1 rescued such inhibition and abrogated the upregulated expression of phosphorylation p38 MAPK. The p38 MAPK inhibitor (SB203580) showed a similar effect with Rg1 and attenuated the LPS-induced inhibition of ZO-1, occludin and claudin-1 expression, which is consistent with the reduced expression of NLRP3 inflammasome and IL-1ß. Furthermore, the specific inhibitors of NLRP3 and IL-1ß result in increased expression of tight-junction-related protein, demonstrating that p38 MAPK signaling was associated with Rg1 suppression of tight junction disruption. Besides, LPS treatment decreased the expression of ZO-1, occludin and claudin-1 through p38 MAPK signaling, and caused abnormal morphological changes in murine ileum. Meanwhile, Rg1 attenuated the decreased expression of ZO-1, occludin and claudin-1 and partially alleviated LPS-induced morphological changes in murine ileum. In summary, these findings characterized a novel mechanism by which Rg1 alleviates LPS-induced intestinal tight junction disruption by inhibiting the p38 MAPK-mediated NLRP3 inflammasome pathway.

Low-concentration iron promotes Klebsiella pneumoniae biofilm formation by suppressing succinic acid.

BACKGROUND: Klebsiella pneumoniae is widely distributed in water and plays a major role in both human and poultry infections. Many K. pneumoniae strains form biofilms on various surfaces, enhancing their pathogenicity and resistance to antibiotics. The water supply pipeline of chicken farms has become a hotbed for the growth of K pneumoniae biofilm because of its humid environment, and because the chicken drinking water pipeline is thin, it is easily blocked by the biofilm, and the diffused cells can cause repeated and persistent infections. Iron is vital to the growth of microorganisms and the formation of biofilms. Therefore, the aim of this study was to examine the effects of iron on K. pneumoniae biofilm formation and any associated metabolic changes to provide a rationale for reducing the formation of biofilms. RESULTS: Biofilm formation was enhanced to the greatest extent by the presence of 0.16 mM FeCl2, producing a denser structure under electron microscopy. The number of biofilm-forming and planktonic bacteria did not change, but protein and polysaccharide concentrations in the bacterial extracellular polymeric substances (EPS) were significantly increased by iron supplementation. To clarify this mechanism, intracellular metabolomic analysis was carried out, showing that the differential, down-regulated metabolites included succinic acid. The addition of 1.7 mM succinic acid counteracted the biofilm-forming effect of iron, with no bactericidal side effects. CONCLUSION: This study demonstrates the importance of succinic acid and iron in K. pneumoniae biofilms, and provides insight into the formation of K. pneumoniae biofilms and direction for the development of new antibacterial agents.

In vivo Pharmacokinetic/Pharmacodynamic (PK/PD) Profiles of Tulathromycin in an Experimental Intraperitoneal Haemophilus parasuis Infection Model in Neutropenic Guinea Pigs.

Tulathromycin is a semi-synthetic macrolide antimicrobial that has an important role in veterinary medicine for respiratory disease. The objective of the study was to develop a pharmacokinetic/pharmacodynamic (PK/PD) model to examine the efficacy and determine an optimal dosage of tulathromycin intramuscular (IM) treatment against Haemophilus parasuis infection induced after intraperitoneal inoculation in neutropenic guinea pigs. The PKs of tulathromycin in serum and lung tissue after intramuscular administration at doses of 1, 10, and 20 mg/kg in H. parasuis-infected neutropenic guinea pigs were evaluated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The tulathromycin minimum inhibitory concentration (MIC) against H. parasuis was ~16 times lower in guinea pig serum (0.03 µg/mL) than in cation-adjusted Mueller-Hinton broth (CAMHB) (0.5 µg/mL). The ratio of the 168-h area under the concentration-time curve (AUC) to MIC (AUC168h/MIC) positively correlated with the in vivo antibacterial effectiveness of tulathromycin (R 2 = 0.9878 in serum and R 2 = 0.9911 in lung tissue). The computed doses to achieve a reduction of 2-log10 CFU/lung from the ratios of AUC72h/MIC were 5.7 mg/kg for serum and 2.5 mg/kg for lung tissue, which lower than the values of 13.2 mg/kg for serum and 8.9 mg/kg for lung tissue with AUC168h/MIC. In addition, using as objective a 2-log10 reduction and an AUC0-72h as the value of the PK/PD index could be more realistic. The results of this study could provide a solid foundation for the application of PK/PD models in research on macrolide antibiotics used to treat respiratory diseases.

Exogenous Citrulline and Glutamine Contribute to Reverse the Resistance of Salmonella to Apramycin.

Antibiotic resistance is an increasing concern for human and animal health worldwide. Recently, the concept of reverting bacterial resistance by changing the metabolic state of antibiotic-resistant bacteria has emerged. In this study, we investigated the reversal of Apramycin resistance in Salmonella. First, non-targeted metabonomics were used to identify key differential metabolites of drug-resistant bacteria. Then, the reversal effect of exogenous substances was verified in vivo and in vitro. Finally, the underlying mechanism was studied. The results showed that the metabolites citrulline and glutamine were significantly reduced in Apramycin-resistant Salmonella. When citrulline and glutamine were added to the culture medium of drug-resistant Salmonella, the killing effect of Apramycin was restored markedly. Mechanistic studies showed that citrulline and glutamine promoted the Tricarboxylic acid cycle, produced more NADH in the bacteria, and increased the proton-motive force, thus promoting Apramycin entry into the bacterial cells, and killing the drug-resistant bacteria. This study provides a useful method to manage infections by antibiotic-resistant bacteria.

Synthesis and antimicrobial activity of the hybrid molecules between amoxicillin and derivatives of benzoic acid.

Due to the increasing problem of bacterial resistance worldwide, the demand for new antibiotics is becoming increasingly urgent. We wished to: (a) prepare hybrid molecules by linking different pharmacophores by chemical bonds; (b) investigate the antib acterial activity of these hybrids using drug-sensitive and drug-resistant pathogens in vitro and vivo. A series of hybrid molecules with a diester structure were designed and synthesized that linked amoxicillin and derivatives of benzoic acid via a methylene bridge. Synthesized compounds were evaluated for activities against Gram-positive bacteria (Staphylococcus aureus American Type Culture Collection [ATCC] 29213, ATCC 11632; methicillin-resistant S. aureus [MRSA] 11; Escherichia coli ATCC 25922) and Gram-negative bacteria (Salmonella LS677, GD836, GD828, GD3625) by microdilution of broth. Synthesized compounds showed good activity against Gram-positive and Gram-negative bacteria in vitro. In particular, amoxicillin-p-nitrobenzoic acid (6d) showed good activity against Salmonella species and had better activity against methicillin-resistant S. aureus (minimum inhibitory concentration [MIC] = 64 µg/ml) than the reference drug, amoxicillin (MIC = 128 µg/ml). Amoxicillin-p-methoxybenzoic acid (6b) had the best antibacterial activity in vivo (ED50 = 13.2496 µg/ml). The hybrid molecules of amoxicillin and derivatives of benzoic acid synthesized based on a diester structure can improve the activity of amoxicillin against Salmonella species and even improve the activity against MRSA.

Increased Antimicrobial Activity of Colistin in Combination With Gamithromycin Against Pasteurella multocida in a Neutropenic Murine Lung Infection Model.

We investigate the antimicrobial activity of combined colistin and gamithromycin against nine Pasteurella multocida strains by testing in vitro susceptibility. Two high-colistin minimal inhibitory concentration (MIC) isolates (D18 and T5) and one low-colistin MIC isolate (WJ11) were used in time-kill tests and therapeutic effect experiments using a neutropenic murine pneumonia model over 24 h. Pharmacokinetics (PK) in plasma was calculated along with pharmacodynamics (PD) to determine the PK/PD index. Synergy between colistin and gamithromycin was observed using high-colistin MIC isolates, equating to a 128- or 256-fold and 4- or 8-fold reduction in colistin and gamithromycin concentration, respectively. Interestingly, no synergistic effect of the combination on low-colistin MIC isolates was observed. However, regardless of the MIC difference among isolates, each drug tended to reach the same concentration in all isolates subjected to combined treatments, which was verified by the time-kill tests presenting similar rates and extent of killing for isolates D18, T5, and WJ11. The AUC( 0 - 24 h)/MIC index was used to evaluate the relationship between PK and PD, and the correlation was >0.89. The relevant gamithromycin doses for combined therapy were determined, and the value decreased from 6- to 35-fold compared with monotherapy. Combined colistin and gamithromycin therapy provides a more potent therapeutic regimen than monotherapy against P. multocida strains.

Environmental remodeling of human gut microbiota and antibiotic resistome in livestock farms.

Anthropogenic environments have been implicated in enrichment and exchange of antibiotic resistance genes and bacteria. Here we study the impact of confined and controlled swine farm environments on temporal changes in the gut microbiome and resistome of veterinary students with occupational exposure for 3 months. By analyzing 16S rRNA and whole metagenome shotgun sequencing data in tandem with culture-based methods, we show that farm exposure shapes the gut microbiome of students, resulting in enrichment of potentially pathogenic taxa and antimicrobial resistance genes. Comparison of students' gut microbiomes and resistomes to farm workers' and environmental samples revealed extensive sharing of resistance genes and bacteria following exposure and after three months of their visit. Notably, antibiotic resistance genes were found in similar genetic contexts in student samples and farm environmental samples. Dynamic Bayesian network modeling predicted that the observed changes partially reverse over a 4-6 month period. Our results indicate that acute changes in a human's living environment can persistently shape their gut microbiota and antibiotic resistome.

Assessing Global Human Exposure to T-2 Toxin via Poultry Meat Consumption Using a Lifetime Physiologically Based Pharmacokinetic Model.

Residue depletion of T-2 toxin in chickens after oral gavage at 2.0 mg/kg twice daily for 2 days was determined in this study. A flow-limited physiologically based pharmacokinetic (PBPK) model was developed for lifetime exposure assessment in chickens. The model was calibrated with data from the residue depletion study and then validated with independent data. A local sensitivity analysis was performed, and 16 sensitive parameters were subjected to Monte Carlo analysis. The population PBPK model was applied to estimate daily intake values of T-2 toxin in different countries based on reported consumption factors and the guidance value of 0.25 mg/kg in feed for chickens by the European Food Safety Authority (EFSA). The predicted daily intakes in different countries were all lower than the EFSA's total daily intake, suggesting that the EFSA's guidance value has minimal risk. This model provides a foundation for scaling to other mycotoxins and other food animal species.

A novel experimental intraperitoneal infection model for Haemophilus parasuis in neutropenic guinea pigs.

INTRODUCTION: Haemophilus parasuis, one of the major swine pathogens, has at least fifteen different types, all of which have significant economic effects on the global swine industry. The aim of this study was to establish an experimental intraperitoneal infection model for H. parasuis in neutropenic guinea pigs. METHODS: Intraperitoneal administration of cyclophosphamide and Haemophilus parasuis was conducted in guinea pigs. Clinical signs, gross pathology, and histopathology were observed in neutropenic guinea pigs infected with H. parasuis. RESULTS: Intraperitoneal administration of 100 mg/kg cyclophosphamide led to immunosuppression with white blood cells, lymphocytes, and neutrophils all <1000 mm3, while no histological tissue damage was observed. Intraperitoneal administration of 109 colony-forming units (CFU) of H. parasuis led to typical respiratory symptoms, 90% morbidity, and 20% mortality in a 72 h-period. Bacteriological screening revealed that multiple organs, including the heart, liver, spleen, lungs, kidneys, and blood, were infected with H. parasuis. The threshold loads of bacteria in blood and the lungs were (7.04 ±â€¯0.53)log10 CFU/mL and (6.24 ±â€¯0.62)log10 CFU/g, respectively, at 3 d after infection. Gross pathology examination showed celiac effusion, intestinal mucosal hemorrhage, and liver, spleen, or lung swelling, necrosis, and hemorrhage. Congestion, mild interstitial pneumonia, inflammatory exudation, and endothelial cell proliferation were observed in the histological examination. DISCUSSION: All the results suggest that we have established an experimental intraperitoneal infection model for H. parasuis in neutropenic guinea pigs. It is especially useful as a tool for pharmacokinetics, pharmacodynamics, or a pharmacokinetics/pharmacodynamics (PK/PD) model of antimicrobial agents against respiratory disease.

Molecular epidemiology, antimicrobial susceptibility, and pulsed-field gel electrophoresis genotyping of Pseudomonas aeruginosa isolates from mink.

Pseudomonas aeruginosa is an important animal pathogen and contributes to hemorrhagic pneumonia in mink. Between April 2011 and December 2016, samples of lung, liver, and spleen were collected from mink with this disease on 11 mink farms in 5 Chinese provinces. From these samples, we obtained 98 isolates of P. aeruginosa that belonged to 5 serotypes: G (n = 58), I (n = 15), C (n = 8), M (n = 5), and B (n = 2); 10 isolates were not typeable (10/98). More than 90% of the isolates formed biofilms, and 85% produced slime. All 98 isolates were resistant to 10 antibiotics (oxacillin, ampicillin, penicillin G, amoxicillin, ceftriaxone, cefazolin, cefaclor, tilmicosin, tildipirosin, and sulfonamide). However, almost all were susceptible to gentamicin, polymyxin B, and amikacin. We identified 56 unique genotypes by pulsed-field gel electrophoresis. These findings have revealed genetic diversity and high antimicrobial resistance in P. aeruginosa isolated from mink with hemorrhagic pneumonia and will facilitate the prevention and control of this disease.

Pseudomonas aeruginosa est un agent pathogène animal important et contribue à la pneumonie hémorragique du vison. Entre avril 2011 et décembre 2016, des échantillons de poumon, foie, et rate ont été prélevés de visons avec cette condition dans 11 élevages retrouvés dans cinq provinces chinoises. À partir de ces échantillons nous avons obtenu 98 isolats de P. aeruginosa qui appartenaient à cinq sérotypes : G (n = 58), I (n = 15), C (n = 8), M (n = 5), et B (n = 2); 10 isolats étaient non-typables (10/98). Plus de 90 % des isolats produisaient du biofilm, et 85 % produisaient de la substance visqueuse. Les 98 isolats étaient résistants à 10 antibiotiques (oxacilline, ampicilline, pénicilline G, amoxicilline, ceftriaxone, céfazolin, céfaclor, tilmicosine, tildipirosine, et sulfonamide). Toutefois, presque tous étaient sensibles à la gentamycine, la polymyxine B, et l'amikacine. Nous avons identifié 56 génotypes uniques par électrophorèse en champs pulsés. Ces résultats ont révélé une diversité génétique et une résistance élevée aux antibiotiques chez les isolats de P. aeruginosa provenant de visons avec la pneumonie hémorragique et faciliteront la prévention et la maitrise de cette maladie.(Traduit par Docteur Serge Messier).

Synergistic Antimicrobial Activity of Colistin in Combination with Rifampin and Azithromycin against Escherichia coli Producing MCR-1.

The lack of available antibiotics is a global public health problem due to the emergence of antimicrobial resistance. Effective therapeutic regimens are urgently needed against Escherichia coli strains that produce the colistin resistance gene mcr-1 and to inhibit the emergence of resistance. In this study, we assessed the antimicrobial activity of a series of concentrations of colistin-based combinations with rifampin and/or azithromycin against three strains of Escherichia coli, including colistin-resistant isolate MZ1501R, isolate HE1704R that produces MCR-1, and colistin-susceptible isolate MZ1509S Experiments were conducted with a medium inoculum of ∼107 CFU/ml over 48 h. Subsequently, the in vivo therapeutic effect was investigated using a neutropenic mouse thigh infection model. Almost all monotherapies showed unsatisfactory antibacterial activity against E. coli isolates producing MCR-1. In contrast, colistin in combination with rifampin or azithromycin resulted in an obvious decrease in the bacterial burden albeit with regrowth. More obviously, synergistic antimicrobial activity of colistin-based triple-combination therapy with rifampin and azithromycin was observed, resulting in a rapid and exhaustive antibacterial effect. In vivo treatments confirmed these findings, where mean decreases of 0.38 to 0.90 log10 CFU and 1.27 to 1.78 log10 CFU were noted after 24 h and 48 h of treatment, respectively, against colistin-resistant E. coli strains when 5 mg/kg of body weight of colistin was combined with rifampin and azithromycin. Colistin-based combinations with rifampin and azithromycin provide a more active therapeutic regimen than monotherapy or colistin-based double combinations against E. coli producing MCR-1.

Epidemiology of Haemophilus parasuis isolates from pigs in China using serotyping, antimicrobial susceptibility, biofilm formation and ERIC-PCR genotyping.

BACKGROUND: Haemophilus parasuis is a commensal organism of the upper respiratory tract of healthy pigs and causes high morbidity and mortality in piglets. The aim of this study was to investigate the epidemiology of H. parasuis in China from 2014 to 2017. METHODS: We characterized 143 H. parasuis isolates by serotyping, antimicrobial susceptibility, biofilm formation and with enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) assays. RESULTS: Serotyping revealed serovar 5 as the most prevalent (26.6%) followed by serovars 4 (22.4%), 7 (9.1 %), 13 (6.3%), 12 (5.6 %), and non-typeable (8.4%). In a panel of 23 antimicrobials, the minimum inhibitory concentration 50% (MIC50) were in the range of 0.25-16 µg/mL and MIC90 were 2->512 µg/mL. A total of 99 isolates of H. parasuis (69.2%) were able to form biofilms and 59.6% (59/99) performed weak biofilm-forming ability. ERIC-PCR revealed a very heterogeneous pattern with 87 clusters. DISCUSSION: These H. parasuis isolates showed a high serovar and genotypic lineage diversity, different abilities to form biofilms and a high degree of genetic diversity. Biofilm formation was related to antimicrobial susceptibility but there were no statistically significant associations between the antimicrobial susceptibility and either the serovars or the ERIC-PCR clusters. This study showed a high prevalence of high-MIC H. parasuis strains and suggests the need for a continuous surveillance of clinical isolates of H. parasuis.